Make CI tests not fail

[dmunozv04]

Makes tests work again, since the latest ubuntu version doesn't have python3.6 support.

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[aarranz]

@dmunozv04, tests are still failing. Any progress on this?

[dmunozv04]

@aarranz making tests run again has been a bigger task than it looked, since some selenium methods have changed; but I'll have a commit with the fixes soon

[aarranz]

Why upgrading pyScss?

[dmunozv04]

The version on pypi is incompatible with python 3.11
Kronuz/pyScss#428

[aarranz]

Working => merged.